Describe proper use of constrained types in their doc comments

I have the following definition in my schema:

"ID": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "$id": "https://raw.githubusercontent.com/flexiblepower/s2-ws-json/main/s2-json-schema/schemas/ID",
    "title": "ID",
    "type": "string",
    "pattern": "[a-zA-Z0-9\\-_:]{2,64}",
    "description": "An identifier expressed as a UUID"
}

Using import_types! to generate structs for this results in the following type:

pub struct Id(String);

This tuple struct has a private field, which means that it can't easily be constructed outside of the module it's defined in, i.e. trying to create an Id("abcd-1234".to_string()) gives the error tuple struct constructor Id is private.

I would expect the fields of generated tuple structs to be public, just like the fields of regular generated structs. I can work around this by defining a new function for types where this happens, but would prefer to use the types as-is.

Trace the import_types! path that generates the Id tuple struct, then compare its field visibility with regular generated structs. Done means a generated constrained type can be constructed outside its defining module, while preserving the documented constrained-type behavior.